68 Professor W. E. Ayrtori [March 24, 



least 50 per cent, to the amount of coal burned. But there is another 

 most serious objection to the engines, perhaps even more important 

 than the preceding. The heavy engine passing over every part of the 

 line necessitates the whole line and all the bridges being made many 

 times as strong, and therefore many times as costly, and the expense 

 of maintenance consequently also far greater, than if there were no 

 locomotive. And it is not possible to make the ejigine much lighter ; 

 for it would not have then sufficient adhesion with the rails to be able 

 to draw the train ; in fact, you cannot diminish the weight as long as 

 the train is propelled with only one or two pair of driving wheels as 

 at present. The employment of electricity, however, will enable a train 

 to be driven with every pair of wheels, just as the employment of 

 compressed air enables every pair of wheels to brake the train. 



To propel a train we must either utilise the energy of coal by 

 burning it, or use the energy possessed by a mountain stream, or the 

 energy stored up in chemicals, and which is given out when the 

 chemicals are allowed to combine, or we must employ the energy of 

 the wind. Practically we employ at present only the first store for 

 propelling railway trains — the potential energy of coal ; and that is 

 to a great extent the store on which we shall still draw, even when 

 we employ Electric Eailways. For experience shows that, with the 

 modern steam-engine and dynamo, at least one-twentieth of the energy 

 in coal can be converted into electric energy ; and that this is at least 

 twenty times as economical as the direct conversion of the energy of 

 zinc into electric energy by burning it in a galvanic battery. 



But it may be asked, did not Faraday's discovery, in 1831, that a 

 current could be produced by the relative motion of a magnet and a 

 coil of wire, settle this j^oint half a century ago? Theoretically — 

 yes ; practically, however, the problem was very far from being solved, 

 because the dynamo machine was very unsatisfactory, and it was not 

 until Pacinotti, in 1860, suggested the solution of the problem of 

 obtaining a practically continuous current from a number of inter- 

 mittent currents, and until Gramme, about 1870, carried out Pacinotti's 

 suggestion in the actual construction of large working machines, that 

 the mechanical production of currents became commercially possible. 

 [Experiments were then shown illustrating the complete electric trans- 

 mission of power, a gas-engine on the platform giving rapid motion 

 to a magneto-electric machine, and the current thereby produced sent 

 through an electro-motor at the other end of the room, which worked 

 an ordinary lathe.] 



In electric transmission of power there is not only waste of power 

 from mechanical friction, but also from electric friction arising from 

 the electric current heating the wire, through which it passed. 



It was then explained and demonstrated experimentally that this 

 latter waste could be made extremely small by placing so light a 

 load on the electro-motor, that it ran nearly as fast as the generator or 

 dynamo, which converted the mechanical energy into electric energy ; 

 actual experiments leading to the result that for every foot-pound of 



